Switching arrangement for telephone plants



July 19, 1932- K. H. BLOMBERG ET AL 1,868,378

SWITCHING ARRANGEMENT FOR TELEPHONE PLANTS Filed March 13, 1931 2 Sheets-Sheet 1 Patented July 19, 1932 UNITED STATES PATENT OFFICE KNUT HT J'GO BLOIVIBERG, OF APPELVIKEN, AND STEN DANIEL VIGREN, OF STOCKHOLM,

, SWEDEN, ASSIGNORS TO TELEFONAKTIEBOLAGET L. M.

SWEDEN, A COMPANY OF SWEDEN EBICSSON, OF STOCKHOLM,

SWITCHING- ARRANGEMENT FOR TELEPHONE PLAN TS App1icationfiled March 13, 1931, Serial No. 522,462, and in Sweden March 21, 1930.

The present invention relates to switching arrangements in telephone plants to which paystations or coin collector telephone stations are connected. It relates more particu- 5 larly to pay stations of the kind in which the payment or debiting operation for the call is made by the Calling person Without the control of any operator. Such apparatus are commonly so disposed that after the pay station has been connected to the wanted subscriber the calling person is able to hear the reply of the called party but cannot make his own speech audible to the called subscriber before he has actuated the paying or debiting device of the pay station, for example by means of a push button, the previously inserted coins being then dropped into a coin box or a callmeter being moved forward or any other charging or debiting operation being performed. The blocking of speech from'the pay station has generally been brought about by rendering the microphone of the pay station currentless by a short circuit or in another manner.

In previously known apparatus of this kind the blocking of the speaking device in a pay station takes place already upon the .liiting'of the microtelephone when making a call or else-in certain automatic apparatus after the calling person has dialled the wanted number on the finger disc. In manual apparatus and in ordering long distance call or the like in automatic apparatus, the calling person must, however, always speak with an 9 operator. The speaking device in the pay station must then operate normally and to render this possible in known systems it has been necessary to provide complicated switching arrangements, such as special switches, at the operators desk for removing the short circuit or the like.

According to the present invention said inconveniences are eliminated in a simple manner by taking such steps that the calling 45 person is enabled to speak with the operator,

when calling up the telephone exchange and ordering the call whereas his speech is blocke'd'by automatic shiftings in the connections taking place during a period falling between the moment when the connection to the wanted subscriber is completed and up to the moment when the called subscriber responds to the call which blocking can be removed by the calling person only by properly actuating the paying device in the pay station.

On the accompanying drawings, Figures 1 to 4, some embodiments of the invention are shown. In the figures the character A designates the pay station which includes a paying or debiting device D in addition to the parts appertaining to an ordinary telephone apparatus. Said paying device is adapted to be actuated by the calling person by means of for example a push button. Upon actuating the paying device, the previously inserted coin is dropped down into the coin box or a call meter is brought forward or some other similar operation performed. The pay station is connected to the exchange over the line L. The exchange equipment appertaining to said line is enclosed within a rectangle C in dash and dot 'lines on the drawings.

Figure l shows the switching diagram for an embodiment of the invention applied to the manual system of L. M. Ericsson. The

line L terminates in the exchange in a curexample has inserted the prescribed fee and then lifts the microtelephone without actuating the push button of the paying or debiting device D'the current feed relay SR is ill ' switch EOE, the third wire 0, the lower:

Winding of the relaySVRtwhich winding has a low resistance, the cutoff relay BR, and

follows. "When the relay SVR .up'on sending the ringing signal is energized in'the same manner as described in conjunction with the plus'pole. The relay SVR is so adjusted that its armature will not be attracted by this current whereas the armature-ofthecut off;

relay BB is attracted and opens a contact 10, the lamp AL being then putoff, and closes the contact 11 whereby therelay receives holding current over the contact 9. j p

The callingpersonmay now ask the operator for thewanted number. The operator then establishes the talking connectionexholding circuit is closed. The plus pole, the

actly as in an ordinary localfcall and sends ringingv current to the wanted subscriber by pushing down the switch EOE. When the contact 14 in the switch'is closed the following current path is formed. The pluspole,

' the resistance SRR, the third wire 0, the winding of the relay SVR having low re,

sistance, the contact 11, the contact 9,'and the minus pole. The resistance SRR is so small that'the relay SVRreceives sufficientcurrent for attracting itsarmature. When the relay. SVR is energized the followin contact 12, the upper winding'of the relay having high resistance, the contact 18, and

i the minus pole.

Upon attract-ing its armature, the relay SVR opens the contacts 1 and l closes the contacts and 8 whereby the current direction throughthe apparatus. is reversed A blocking device for outgoing speech from the nearly zero or any other' device for the same purpose. I 1

When. the called subscriberlreplies, the

[calling personi's able to hear but cannot V speak to the called party unless he pushes down the button of the paying'device 1). Then the contacts 2, 3 are opened andthe contacts 6, 7 closed whereby the currentrdirection in the apparatus is reversed to'the normal direction. The blocking device is then put out of operation and completetalking connection: established. The contact group actuated by the button of the paying device remains closed until thecalling person after completed call hooks up his microtelephone. When the operator after the clean ing signal removes the cord-the relays are restored to normal position. I

Figure 2 shows a switching diagram for a similar embodiment of the invention. In-

stead of reversing the current direction of the line of the pay station upon ringing current being sent by the operator tothe wanted subscriber, the microphone in the pay station is in this case rendered currentless by disconnecting the central battery from the pay station. The switching operation will be as Figure 1 the contact 1 is opened and the contact 7 closed. Hereby the relay TB is connected to the line branch at the same time as the microphone of the pay station becomes currentless. Then the calling person can not speak with the called subscriber when the latter replies unless he actuates' the paying device D the paystation. VVhen'this is done the following current path'is closed; Earth, acontact 9 in theplaying device, the

line branch' Z), the Contact 7, therelay TR,

and the minus pole. At the same time earth is also connected to the line branch at so that the microphone is shunted. Therela y'TR is energized and closes the contact 8fthe following current path being thenesta'blished. T 1e minus pole, the contact 8, the contact 5,

the resistance 1', and the plus pole. The holding winding ofthe relay SVR is then shortcircuited, so that the relay is deenergized.

,The contact 7 isropened and the contact 1 "closed whereby the pay station again receives microphone current and full talking connec tion is again established. 7

Figuref3 shows the switching diagram'for another" embodiment of the invention. A

completed connection to the wanted 'sub scriber established by an operator or by automatic selectors is shown on the drawing; To block speech in the direction. from the pay station an electronic valve E included in the connection is here disposed in theexchange. Said blocking device is connected up first when the called subscriber B lifts his microtelephone'. o

The switching operation will be the following. WVhen thecalled subscriber B lifts his microtelepho'ne"tofreply to the call the following current path is formed. The plus pole, the one winding of the current feed relay BSR, the line branch (5, thetelephone apparatus B, the line branch. 7;, the other winding'of the. relay B8B, and the minus pole. TheHrelayBS R is energized the following current. path being then formed The plus.pole, the contact l, the relay SVR, the contact 2, and the minus pole. relay SVR then islenergized the contacts '5, 6

When the are opened whereby the direct connection between the pay station A and the subscriber B is-interrupted. At the contacts 3 and 4 the electronic valve E having three electrodes is instead connected into the connection. The subscribers B line is interconnected over condensers C between the control grid and the filament of the valve and the line of the pay station over condensers 0 between the anode and the filament of the valve. Hereby speech currents may pass only from the subscriber B to the pay station but not in the opposite direction.

V] hen the calling person in the pay station has heard the reply of the wanted subscriber he actuates the paying device D and a con tact 13 is opened for a moment and av resistance SR series connected with the line. The current through the current feed relays SR and SR energized upon the call is then reduced to such a degree that the relay SR drops its armature whereas the relay SR still holds its armature. The following cur rent path is then established. The plus pole, the contact 8, the contact 9, the relay TR, and theminus pole. The relay TR is energized and receives calling current over the contacts 10 and 11 and the contact 12. So long as the relay TB is energized the contact 2 is opened which results in that the relay SVR is deenergized whereby the contacts 3 and 4 are opened and the contacts 5 and 6 closed. The electronic valve is thus disconnected and the line of the pay station again joined with the wanted subscribers line in a complete talking connection. This condition lasts until both subscribers have completed their conversa- I and interconnects a speech blocking device E between the two lines which device may consist of the electronic valve shown in Figure 3. Upon sending signal current the following current path is formed. The plus pole, the relaySRR, the contact 14 of the switch EOE, the third wire 0, the one winding of the relay SR, and the minus pole. Said relay SR is energized and receives'holding current over the following path. The minus pole, the lower winding of the relay SR, and the minus pole. When the armature of the relay SR is attracted a current path is formed over the contact 1, the line branch (L, the induction coil 1, the telephone receiver H, the contact 13 in the paying device D, the line branch I), the contact 2, the upper winding of the relay SR,

and theplus pole. The contacts 3 and 4: are interrupted and the contacts 5 and 6 closed so that-the complete talking connection is interruptedand the speech blocking device E connected into circuit. VVh'en the called subscriber replies the calling person can hear'but 'not speak with the called subscriber unless he actuates this paying device D. Then the line-circuit is'interrupted for a moment, the relay SR deenergized, the contacts 5 and 6 opened, the contacts 3 and'el closed, and a complete talking connection established.

As is readily understood the speech block- 'ing' devices shown in conjunction with different exchange equipments may be arbitrarily applied both to manual and automatic systems without receding from the idea of the invention.

We claim 1. A telephone system comprising a pay station, a wanted subscribers station, an exchange, means for establishing a connection from the pay station to the wanted subscribers station, means disposed in the exchange and associated with the connection for the unidirectional and automatic blocking of speech currents from the pay station to the wanted subscribers station prior to payment and for the allowance of speech currents in both directions upon payment.

2. A telephone system comprising a pay station, a wanted subscribers station, an exchange, means in the exchange for the unidirectional blocking of speech currents from the pay station to the wanted subscriber, relay means disposed in the exchange for making said blocking means operative prior to payment and inoperative upon payment.

3. A telephone system comprising a pay station, a wanted subscribers station, an exchange, means in the exchange for the unidirectional blocking of speech currents, from the pay station to the wanted subscriber, relay means disposed in the exchange for making said blocking means operative prior to payment upon the sending of ringing current to the wanted subscriber and inoperative upon payment.

4. A telephone system comprising a pay station, a wanted subscribers station, an exchange, means in the exchange for the unidirectional blocking of speech currents from the pay station to the wanted subscriber, relay means disposed in the exchange for making said blocking means operative prior to payment upon the lifting of the wanted subscribers microtelephone and inoperative upon payment.

5. A telephone system comprising a pay station, a wanted subscribers station, an exchange, a direct current feed circuit from the exchange to the pay station, a switch included in the exchange in said circuit, automatic means for actuating said switch to open the circuit prior to payment and to-elose said circuit upon payment.

6.'A telephone system comprising a, pay I station, a Wanted subscribers station, an exchange means for the establishment of a, connection between the pay station and the Wanted subsoribers set,'e1ectron valve means, autor matic means for including said valve means into said connection and assoc atlng the valve grid with the Wanted subscriber and the valve anode with the pay station prior to payment,

and for removing said valve means from the connection upon payment. y

In testimony whereof We afiix our signatures. e 1

KNUT HUGO BLOMBERG. STEN DANIEL VIGREN. 

